Structural energy storage assemblies and methods for production thereof

ABSTRACT

Described herein are multi-functional composite materials containing energy storage assemblies that can be significantly resistant to tension/compression stress. The energy storage assemblies can contain at least one energy storage layer that contains an insulating layer having a plurality of openings arranged in a spaced apart manner, and a plurality of energy storage devices, each energy storage device being contained within one of the openings. The energy storage devices can be electrically connected to one another. The energy storage layer can contain a support material upon which electrical connections are formed. One or more energy storage layers can be disposed between two or more stress carrying layers to form an energy storage assembly that can have significant resistance to tension/compression stress. Energy storage devices suitable for use in the energy storage assemblies can include, for example, batteries, capacitors and/or supercapacitors. Methods for producing the energy storage assemblies are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119from U.S. Provisional Patent Application Ser. No. 61/378,378, filed Aug.30, 2010, which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention generally relates to energy storage, and, morespecifically, energy storage within a structural energy storageassembly.

BACKGROUND

Multi-functional composite materials have been the subject ofconsiderable research interest as a result of steadily increasing demandfor consumer, industrial and military products having improvedperformance and functionality. Specifically, composite materials havingat least one specialized function, in addition to providing simplestructural support and/or mechanical strength, have been particularlysought out by the engineering community in order to address theforegoing demand for high performance products. One particularlydesirable multi-functional composite material that has been the subjectof intense research is an assembly that provides both an energy storagemedium and significant structural support. Although various approacheshave been applied toward development of such multi-functional compositematerials having energy storage capabilities, research efforts to datehave failed to realize an adequate combination of strength, chargestorage capacity and/or charge storage density, and manufacturing ease.

Certain high performance materials, including carbon nanotubes, havebeen proposed for use in multi-functional composite materials due totheir high mechanical strength, large effective surface area, andelectrical conductivity. Although carbon nanotubes offer significantpotential for developing multi-functional composite materials, researchefforts to date have failed to deliver on the promise offered by theseentities. In a like manner, carbon nanotubes can offer the potential tosignificantly enhance the properties of electrical storage devices suchas, for example, batteries and supercapacitors. In this regard, carbonnanotubes can be used to replace carbon black and/or electrode materialsof conventional electrical storage devices in order to lessen theirweight and/or to improve their charge storage properties.

In view of the foregoing, multi-functional composite materials thatprovide both good structural support and energy storage capabilitieswould be of significant benefit in the art. The present inventionsatisfies this need and provides related advantages as well.

SUMMARY

In some embodiments, energy storage assemblies are described herein. Theenergy storage assemblies contain at least one energy storage layer thatcontains an insulating layer having a plurality of openings arranged ina spaced apart manner, and a plurality of energy storage devices, whereeach energy storage device is contained within one of the openings. Theplurality of energy storage devices are electrically connected to oneanother.

In some embodiments, the energy storage assemblies described hereincontain at least two stress carrying layers and at least one energystorage layer disposed between the at least two stress carrying layers.The at least one energy storage layer contains a support material, aninsulating layer having a plurality of openings arranged in a spacedapart manner, and a plurality of energy storage devices, where eachenergy storage device is contained within one of the openings.

In some embodiments, methods described herein include disposing aplurality of energy storage devices on a support material in a spacedapart manner, and disposing an insulator layer around the plurality ofenergy storage devices on the support material, thereby forming anenergy storage layer.

The foregoing has outlined rather broadly the features of the presentdisclosure in order that the detailed description that follows can bebetter understood. Additional features and advantages of the disclosurewill be described hereinafter, which form the subject of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionsto be taken in conjunction with the accompanying drawings describingspecific embodiments of the disclosure, wherein:

FIG. 1 shows an illustrative schematic of a beam under a load;

FIG. 2 shows an illustrative isometric schematic of a traditionallayered composite material containing an insulating layer and two stresscarrying layers;

FIG. 3A shows an illustrative isometric schematic of an insulating layerin which a plurality of holes have been opened therein; FIG. 3B shows anillustrative isometric schematic of an insulating layer in which aplurality of depressions have been opened therein;

FIG. 4A shows an illustrative schematic of a printed circuit boardhaving series electrical connections and parallel electrical connectionsprinted thereon; FIG. 4B shows an illustrative schematic of the printedcircuit board of FIG. 4A after depositing a plurality of energy storagedevices thereon; FIG. 4C shows an illustrative schematic of the printedcircuit board of FIG. 4B after depositing an insulating layer about theenergy storage devices;

FIG. 5 shows an illustrative schematic of an energy storage assemblyhaving multiple single-row energy storage layers laid alongside oneanother; and

FIG. 6 shows an illustrative side view schematic of an energy storagelayer in which energy storage device casings form the insulating layer.

DETAILED DESCRIPTION

The present disclosure is directed, in part, to structural energystorage assemblies such as, for example, multi-functional compositematerials. The present disclosure is also directed, in part, to methodsfor making structural energy storage assemblies. Traditional energystorage devices such as, for example, batteries and capacitors can beused in the energy storage assemblies described herein. Optionally, theenergy storage assemblies can make use of energy storage devices thathave been enhanced with carbon nanotubes.

Embodiments described herein take advantage of simple beam theory, abrief discussion of which follows. It is to be recognized that thefollowing discussion of simple beam theory should not be consideredmechanistically limiting. As used herein, the term “beam” refers to asubstantially rigid structural member that is supported on at least itsends and is subject to a transverse shear force that results intension/compression stress in the beam that is perpendicular to theapplied shear force. Although the term “beam” can refer to structuralmembers having a large aspect ratio, it is to be recognized that theterm “beam” should be more broadly construed herein to represent anyrigid structural member that bears a transverse shear force.

FIG. 1 shows an illustrative schematic of a beam 100 under a load.According to simple beam theory, the interior of beam 100 near neutralaxis 101 is under shear stress from load 105, but not under appreciabletension/compression stress 107 and 108, which arises from bending forces106. In contrast, exterior faces 102 of beam 100 experience considerabletension/compression stress 107 and 108 when placed under a load.

In view of the foregoing, it has been advantageously recognizedaccording to the present invention that at least a portion of theinterior of a beam can be replaced with a material that is primarilyfunctional rather than primarily structural. Since the interior of abeam is subject to minimal tension/compression stress, the replacementmaterial needs only to be capable of bearing a shear load in order tomaintain structural integrity comparable to that of an unmodified beam.According to the present embodiments, an energy storage assembly canreplace at least a portion of the interior of a beam in order to producea multi-functional composite material that is capable of storingelectrical charge while maintaining significant resistance totension/compression stress. In addition, by replacing at least a portionof the interior of a beam with a replacement material, the overallweight of the beam can be maintained or reduced relative to that of anunmodified beam, according to some embodiments, while maintainingcomparable structural integrity and gaining advantageous functionalproperties. Although not preferred, if the replacement material isheavier than the beam material, the overall weight of the beam will beincreased.

Replacement of the interior of a beam can be particularly advantageousand facile for layered composite materials (e.g., sandwich-typestructures), containing an energy storage assembly located between attwo stress carrying layers. As used herein, the term “stress carryinglayers” will refer to a material that is capable of bearing significanttension/compression stress, particularly when used as the exteriorlayer(s) of a layered composite material.

A particular advantage of composite materials containing the presentenergy storage assemblies is that an article formed therefrom canexhibit enhanced performance relative to an article lacking an energystorage assembly, while not significantly altering the weight ormechanical properties of the original article. That is, articles can beconstructed using the present energy storage assemblies that have acomparable or reduced weight and like mechanical properties relative toa like article lacking an energy storage assembly. Accordingly, articlesproduced in accordance with the present embodiments can make use of thefunctional energy storage capacity therein so as to have longeroperating times relative to comparable articles lacking an energystorage assembly. Other operational advantages in articles containing anenergy storage assembly can be realized as well.

A further advantage of the present energy storage assemblies is thatthey are highly compatible with traditional manufacturing techniques andmaterials used for preparing layered composite materials. Furthermore,the energy storage assemblies described herein are compatible withcommon energy storage devices such as, for example, traditionalbatteries (e.g., Li-ion batteries) and capacitors, a number ofconfigurations for which are known to one having ordinary skill in theart. Although the energy storage devices used in the present embodimentscan be further enhanced (e.g., by incorporation of carbon nanotubestherein), there is no specific manufacturing requirement to do so.

Still further, the energy storage assemblies described herein are notparticularly limited in scale and can be used to form articles having awide breadth of sizes. Ultimately, the size of the energy storagedevices in an energy storage assembly determines its thickness. As anumber of energy storage device sizes and configurations are availableto one having ordinary skill in the art, a wide array of energy storageassembly sizes and configurations can be prepared. Accordingly, articlesthat are a less than about one millimeter thick to tens or hundreds ofcentimeters thick can be fabricated from the energy storage assemblies.In addition, by stacking the energy storage assemblies, even thickerarticles can be prepared, if desired.

The energy storage assemblies described herein can advantageouslydistribute electric charge storage capacity throughout an article formedtherefrom. That is, the present embodiments can allow an energy storagemedium to be spread throughout an article, as opposed to a like articlehaving a single concentrated energy storage site such as, for example, alarge centralized battery or like energy storage device. By electricallyconnecting decentralized, smaller energy storage devices in seriesand/or parallel in the present embodiments, electrical storageproperties comparable to those of a larger energy storage device can berealized. Although articles containing the present energy storageassemblies can also contain one or more centralized energy storagedevices, the distribution of electric charge storage capacity canrepresent a particular advantage for certain articles.

A number of articles can potentially make use of the present energystorage assemblies. For example, unmanned aerial vehicles (UAVs),airplanes, satellites and hybrid gas-electric vehicles containing thepresent energy storage assemblies could exhibit extended operating timeswithout having their operational integrity significantly impacted. Ingeneral, any article that makes use of a power supply, particularlythose that are formed by composite processing techniques, can makeadvantageous use of the present energy storage assemblies. However,articles that do not conventionally draw or use electric chargethemselves can also make use of the present energy storage assemblies.For example, structural articles such as, for example, pipelines,electrical towers, bridges and buildings can have energy storageassemblies incorporated therein. These structural articles can then beused to acquire and store electricity (e.g., through solar energycollection) until the energy is needed elsewhere. Therefore, the presentenergy storage assemblies can be used to supplement traditionalelectrical grid applications. Likewise, they can be utilized in numerousapplications more traditionally associated with energy collectionincluding, for example, solar energy collection, hydroelectric energycollection, wind farm energy collection, and the like.

As used herein, the term “opening” refers to a vacant space within aninsulating layer. In some embodiments, an opening can be a hole thatextends through the insulating layer. In other embodiments, an openingcan be a depression or void that does not extend completely through theinsulating layer.

As used herein, the term “flexible” refers to the condition of beingable to be bent without breaking.

As used herein, the terms “fiber,” “fiber material,” or “filament”equivalently refer to any material that has a fibrous component as abasic structural feature. As used herein, the term “continuous fibers”refers to spoolable lengths of fiber materials such as individualfilaments, yarns, rovings, tows, tapes, ribbons, woven and non-wovenfabrics, plies, mats, and the like.

As used herein, the term “infused” refers to being bonded and “infusion”refers to the process of bonding. As used herein, the terms “carbonnanotube-infused fiber,” “carbon nanotube-infused fiber material,” or“fibers that are infused with carbon nanotubes” equivalently refer to afiber material that has carbon nanotubes bonded thereto. Such bonding ofcarbon nanotubes to a fiber material can involve mechanical attachment,covalent bonding, ionic bonding, pi-pi interactions (pi-stackinginteractions), and/or van der Waals force-mediated physisorption. Insome embodiments, the carbon nanotubes can be directly bonded to thefiber material. In other embodiments, the carbon nanotubes can beindirectly bonded to the fiber material via a barrier coating and/orcatalytic nanoparticles used to mediate growth of the carbon nanotubes.The particular manner in which the carbon nanotubes are infused to thefiber material can be referred to as the bonding motif.

As used herein, the terms “spoolable lengths” or “spoolable dimensions”equivalently refer to a fiber material that has at least one dimensionthat is not limited in length, thereby allowing the fiber material to bestored on a spool or mandrel. A fiber material of “spoolable lengths” or“spoolable dimensions” has at least one dimension that indicates the useof either batch or continuous processing for carbon nanotube infusionthereon.

As used herein, the term “nanoparticle” refers to particles having adiameter between about 0.1 nm and about 100 nm in equivalent sphericaldiameter, although nanoparticles need not necessarily be spherical inshape. As used herein, the term “catalytic nanoparticle” refers to ananoparticle that possesses catalytic activity for mediating carbonnanotube growth.

As used herein, the term “transition metal” refers to any element oralloy of elements in the d-block of the periodic table (Groups 3 through12), and the term “transition metal salt” refers to any transition metalcompound such as, for example, transition metal oxides, carbides,nitrides, nitrates, sulfides, sulfates, phosphates, halides (e.g.,fluorides, chlorides, bromides, and iodides), acetates, citrates and thelike. Illustrative transition metals that can form catalyticnanoparticles suitable for synthesizing carbon nanotubes include, forexample, Ni, Fe, Co, Mo, Cu, Pt, Au, Ag, alloys thereof, salts thereof,and mixtures thereof.

As used herein, the terms “sizing agent,” or “sizing,” collectivelyrefer to materials used in the manufacture of fiber materials as acoating to protect the integrity of the fiber material, to provideenhanced interfacial interactions between the fiber material and amatrix material, and/or to alter and/or to enhance certain physicalproperties of the fiber material.

As used herein, the term “uniform in length” refers to a condition inwhich carbon nanotubes have lengths with tolerances of plus or minusabout 20% or less of the total carbon nanotube length, for carbonnanotube lengths ranging from about 1 μm to about 500 μm. At very shortcarbon nanotube lengths (e.g., about 1 μm to about 4 μm), the tolerancecan be plus or minus about 1 μm, that is, somewhat more than about 20%of the total carbon nanotube length.

As used herein, the term “uniform in density distribution” refers to acondition in which the carbon nanotube coverage density on a fibermaterial has a tolerance of plus or minus about 10% over the fibermaterial surface area that is covered with carbon nanotubes.

Embodiments described herein make use of at least one energy storagelayer. Such energy storage layers contain at least 1) an insulatinglayer that has a plurality of openings arranged in a spaced apartmanner, and 2) a plurality of energy storage devices, where each energystorage device is contained within one of the openings. Although theenergy storage devices can be accessed separately, if desired, it isgenerally the case that the energy storage devices are electricallyconnected to one another.

According to the present embodiments, the insulating layer of the atleast one energy storage layer can provide the shear strength needed tosuccessfully replace the interior portions of a beam. That is, in atraditional layered composite material, the at least one energy storagelayer can make up at least a portion of the interior of the compositematerial. FIG. 2 shows an illustrative isometric schematic of atraditional layered composite material 200 containing interior layer 201and stress carrying layers 202. It has been surprisingly discovered thata plurality of openings can be disposed within interior layer 201without significantly impacting the layer's shear strength, as discussedin more detail hereinbelow. In addition to maintaining the shearstrength, the disposition of openings within the insulating layer canimprove the flexibility of interior layer 201, which can be furtheradvantageous in the present embodiments. According to the presentembodiments, interior layer 201 can be an electrically insulating layer(e.g., a dielectric material). By placing an energy storage device ineach of the openings within the insulating layer, a multi-functionalcomposite material can be created that is both structurally sound andcapable of energy storage.

In some embodiments, the openings within the insulating layer can be aplurality of holes. FIG. 3A shows an illustrative isometric schematic ofan insulating layer 300 in which a plurality of holes 301 have beenopened therein. The holes extend through the insulating layer. In otherembodiments, the openings within the insulating layer can be a pluralityof depressions. FIG. 3B shows an illustrative isometric schematic of aninsulating layer 302 in which a plurality of depressions 303 have beenopened therein. The depressions extend incompletely through theinsulating layer. Since the incorporation of openings in the insulatinglayer can result in a negligible impact on its shear strength, energystorage devices can be incorporated within the openings in order toinstill functionality into what would otherwise constitute dead weightin a composite material. Although the energy storage devices can enhanceshear strength or another mechanical property of the insulating layer,if desired, there is no requirement for them to do so.

To demonstrate that openings within the interior layer of a compositematerial may not significantly impact its shear strength, preliminarymodeling studies were conducted using an isotropic beam material madefrom aluminum. Modeling studies were conducted with Pro EngineerMechanica software by Parametric Technology Corporation. As a control, a0.07″ thick beam was modeled to determine its weight and maximum stress.For such a beam, the weight was 0.0142 pounds, and the maximum stresswas 1.25 ksi. Next, a 0.08″ thick beam having 0.03″×0.043″×0.43″openings (depressions) every 0.5″ was modeled to determine its weightand maximum stress. In this case, the weight was 0.012 pounds, and themaximum stress was only reduced to 1.11 ksi. Thus, for only a slightlylarger beam, the weight was reduced by ˜15% and the maximum stress wasreduced by only ˜10%. The 15% weight loss can be replaced with energystorage devices according to the present embodiments to produce a beamthat is only marginally thicker and weaker than the original beam. Itshould be noted that the foregoing analysis presents only a preliminaryshowing demonstrating that the maximum stress of an insulating layer canbe largely maintained with openings disposed therein. It is in no mannersuggested that the foregoing dimensions of the openings or the placementthereof represents an optimum arrangement for maintaining stress withinan insulating layer.

Ultimately, the height of the energy storage devices determines theminimum height of the insulating layer. In various embodiments, theheight of the insulating layer can be at least that of the energystorage devices. In some embodiments, the height of the insulating layercan be substantially the same as that of the energy storage devices. Insuch embodiments, the openings in the insulating layer constitute holes,since the insulating layer does not overcoat the energy storage devicesif they are substantially the same height. In other embodiments, theheight of the insulating layer can be greater than that of the energystorage devices. In such embodiments, the openings in the insulatinglayer can be in the form of either holes or depressions. For example, ifthe insulating layer height exceeds the height of the energy storagedevices but does not overcoat them, then the openings can be in the formof holes, with the energy storage devices not completely filling thevolume of the holes. However, if the insulating layer height exceeds theheight of the energy storage devices and overcoats them, then theopenings can be in the form of depressions or voids. In the suchembodiments, the energy storage devices can either completely fill orincompletely fill the volume of the depressions.

In some embodiments, energy storage assemblies described herein cancontain at least one energy storage layer that comprises an insulatinglayer having a plurality of openings arranged in a spaced apart manner,and a plurality of energy storage devices, each being contained withinone of the openings. In the energy storage assemblies, the plurality ofenergy storage devices can be electrically connected to one another. Insome embodiments, the openings can be depressions that extend partiallythrough the insulating layer. In other embodiments, the openings can beholes that extend completely through the insulating layer.

In general, the insulating layer of the present embodiments can be apolymer or a fiber-reinforced polymer composite. As noted above, theinsulating layer can provide structural integrity and shear support tothe energy storage layer. In some embodiments, the fiber reinforcedpolymer composite can be a fiberglass composite. In some embodiments, asuitable polymer for the insulating layer can be a polycarbonate. Otherthermoplastic and thermosetting polymers can be envisioned by one havingordinary skill in the art.

In some embodiments, the energy storage layer can further contain asupport material upon which the plurality of energy storage devices andthe insulating layer are disposed. In general, such support materialscan maintain some degree of flexibility such that the energy storagelayer also is flexible. Such support materials can have at leastsufficient structural integrity to support the plurality of energystorage devices and the insulating layer.

In general, the support material can be relatively thin in comparison tothe height of the energy storage devices and the insulating layer. Thatis, in such embodiments, the support material is thinner than the energystorage device or the insulating layer. In some embodiments, the supportmaterial can be in the form of a structure such as, for example, aflexible wafer or membrane. In some embodiments, the support materialcan be in the form of a flexible ribbon material. In some embodiments,the support material can be a polymer such as, for example, athermoplastic or thermosetting polymer (e.g., an epoxy). In someembodiments, the support material can be a printed circuit boardsubstrate. In such embodiments, the electrical connections between theplurality of energy storage devices can be on the support material.Illustrative printed circuit board substrates can include, for example,dielectric materials that are laminated together with an epoxy resin. Anumber of printed circuit board substrates are known to one havingordinary skill in the art, any of which can be chosen to suit aparticular implementation of the present embodiments.

When disposed on a support material, the energy storage devices can bearranged in single row in some embodiments. In alternative embodiments,multiple rows of the energy storage devices can be arrayed on thesupport material (e.g., a grid structure). In some embodiments, theenergy storage devices within the energy storage layer can be in theform of a grid structure. In forming an energy storage assembly,multiple rows of the energy storage devices can be arrayed in a gridstructure by initially forming the energy storage layer on a supportmaterial having multiple rows of energy storage devices, or by layingmultiple rows of single-row energy storage layers alongside one another(see FIG. 5).

In general, any energy storage device of a suitable size can be used inthe present embodiments. In some embodiments, the energy storage devicescan be batteries. In some embodiments, a suitable battery can be alithium-ion battery. In other embodiments, the energy storage devicescan be capacitors or supercapacitors. In some embodiments, the energystorage devices can be further enhanced with carbon nanotubes.

Electrical connections between the energy storage devices can beestablished through any means known to one having ordinary skill in theart. In some embodiments, at least some of the energy storage devicesare connected in parallel. In some embodiments, at least some of theenergy storage devices are connected in series. In some embodiments, atleast some of the energy storage devices are connected in series and inparallel. One of ordinary skill in the art will recognize that anycombination of series and parallel electrical connections can be used toestablish a desired voltage and current for the energy storage layer inthe present energy storage assemblies.

In some embodiments, electrical connections between the energy storagedevices can be established through electrical connections on a printedcircuit board substrate, which serves as a support material for theenergy storage layer. FIG. 4A shows an illustrative schematic of aprinted circuit board substrate 400 having series electrical connections401 and parallel electrical connections 402 printed thereon. FIG. 4Bshows an illustrative schematic of the printed circuit board substrateof FIG. 4A after depositing a plurality of energy storage devices 404a-404 f thereon. As shown in FIGS. 4A and 4B, energy storage devices 404a-404 f are connected to one another in parallel, where every threeenergy storage devices are also connected to one another in series inorder to step up the voltage. It should be recognized that thearrangement shown in FIGS. 4A and 4B should be considered illustrativein nature only, and any series/parallel arrangement of the energystorage devices can be used in the present embodiments. Particularly,the connection of every three energy storage device in series should notbe considered limiting. FIG. 4C shows an illustrative schematic of theprinted circuit board substrate of FIG. 4B after depositing aninsulating layer 405 about energy storage devices 404 a-404 f to formenergy storage layer 406.

As previously noted, the energy storage layers can be used in layeredcomposite materials to form an energy storage assembly having goodtension/compression stress properties. In such embodiments, the exteriorstress carrying layers of the energy storage assemblies can beartension/compression stress, and the interior energy storage layer(s) canbear shear stress, in addition to conveying electrical storagecapabilities.

In some embodiments, at least one stress carrying layer can be incontact with the at least one energy storage layer. In some embodiments,the at least one energy storage layer can be disposed between at leasttwo stress carrying layers. In such embodiments, the energy storageassemblies resemble layered composite 200 depicted in FIG. 2, exceptthat insulating layer 201 is replaced by insulating layer 300 or 302depicted in FIG. 3A or 3B, respectively, in which energy storage devicesare located in the openings therein. In some embodiments, a suitablestress carrying layer can be a fiber reinforced polymer composite.

In some embodiments, the present energy storage assemblies can havetheir plurality of energy storage devices arranged in a grid structurein the at least one energy storage layer. As noted above, the energystorage layer(s) can be constructed such that multiple rows of energystorage devices are contained therein. Alternately, multiple single-rowenergy storage layers can be laid alongside each other to form a largerenergy storage layer within the energy storage assemblies. FIG. 5 showsan illustrative schematic of an energy storage assembly having multiplesingle-row energy storage layers 501 laid alongside one another. In FIG.5, the stress carrying layers have not been shown for purposes ofclarity.

In some embodiments, the energy storage assemblies can contain multipleenergy storage layers stacked upon one another and disposed between twoor more stress carrying layers. That is, the energy storage layers canbe built up to attain a desired height in an article containing theenergy storage assemblies. Likewise, multiple stress carrying layers canbe used to achieve a desired thickness or strength.

Since tension/compression stress can be substantially borne by thestress carrying layers in the present energy storage assemblies, thethickness of the at least one energy storage layer can be a significantfraction of the thickness of the energy storage assemblies withoutcomprising their structural integrity. In some embodiments, a thicknessof the at least one energy storage layer can be up to about 50% of thethickness of the energy storage assembly. In some embodiments, athickness of the at least one energy storage layer can be up to about60% of the thickness of the energy storage assembly. In someembodiments, a thickness of the at least one energy storage layer can beup to about 70% of the thickness of the energy storage assembly. In someembodiments, a thickness of the at least one energy storage layer can beup to about 80% of the thickness of the energy storage assembly. In someembodiments, a thickness of the at least one energy storage layer can beup to about 90% of the thickness of the energy storage assembly.

In some alternative embodiments, the insulator layer can be derived froma casing enveloping the energy storage devices. In such embodiments, thecasing of the energy storage device can both support and protect theenergy storage device, while also providing resistance against shearforces in an energy storage assembly. FIG. 6 shows an illustrative sideview schematic of an energy storage layer 600 in which energy storagedevice casings form the insulating layer. As shown in FIG. 6, energystorage devices 601 protected by casing 602 are butted against oneanother on support material 603. The resulting energy storage layer 600resembles a compression watch band, where the individual energy storagedevices 601 and their associated casing 602 represent links in the watchband. As will be evident to one having ordinary skill in the art, suchan arrangement of the energy storage devices 601 and casings 602 willmaintain considerable flexibility, as further provided for by supportmaterial 603. It should be pointed out that energy storage layer 600still contains the energy storage devices 601 in a spaced apart manner,since the associated casings 602 are not part of the energy storagedevices themselves. In the embodiment shown in FIG. 6, the energystorage devices 601 are present in a depression within the insulatinglayer, as defined by casing 602. As shown in FIG. 6, the energy storagedevices 601 do not completely fill the void within each casing 602.However, it should be recognized that the energy storage devices 601 cancompletely or incompletely fill the casings 602, depending on the designof both the energy storage devices and casing.

In some embodiments, energy storage assemblies described herein cancontain at least two stress carrying layers and at least one energystorage layer disposed between the at least two stress carrying layers.The at least one energy storage layer can contain a support material, aninsulating layer having a plurality of openings arranged in a spacedapart manner, and a plurality of energy storage devices, where eachenergy storage device is contained within one of the openings.

In some embodiments, methods for forming the present energy storageassemblies are described herein. In some embodiments, the methods caninclude disposing a plurality of energy storage devices on a supportmaterial in a spaced apart manner, and then disposing an insulatinglayer around the plurality of energy storage devices on the supportmaterial to form an energy storage layer. In some embodiments, themethods can further include forming a plurality of electricalconnections on the support material, and then electrically connectingthe plurality of energy storage devices using the plurality ofelectrical connections. In alternative embodiments, the methods caninvolve forming direct electrical connections (e.g., wires and the like)between the energy storage devices.

In some embodiments, the insulating layer of the energy storage layercan be preformed before being placed around the energy storage devices.That is, in such embodiments, the insulating layer can be preformed witha plurality of spaced apart openings that match the spacing of theplurality of energy storage devices on the support material. Patterningof a polymeric or like insulating layer with a plurality of spaced apartopenings can be accomplished by a number of fabrication techniques thatare well known to one having ordinary skill in the art. After formationof the patterned insulating layer, the insulating layer can be laidaround the energy storage devices to form the energy storage layer.

In some embodiments, the present methods can further include placing atleast one of the energy storage layers between at least two stresscarrying layers. In an embodiment, each stress carrying layer can be afiber-reinforced polymer composite. In some embodiments, a single energystorage layer can be placed between the stress carrying layers. In otherembodiments, multiple single-row energy storage layers can be laidalongside one another when being placed between the stress carryinglayers. In still other embodiments, multiple energy storage layers canbe stacked upon one another when being placed between the stresscarrying layers.

In some embodiments, placing the at least one energy storage layerbetween the stress carrying layers can involve a laying up process. Insome embodiments, such a laying up process can involve simply cuttingstrips of the energy storage layer to a desired length and then placinga desired number of strips between the stress carrying layers. It shouldbe noted than when cutting the energy storage layers, it can happen thatan energy storage device is severed during the cutting process. Althoughit is not particularly desirable to cut an energy storage device, it isnot imperative that all energy storage devices remain functional inorder for the energy storage layers to function satisfactorily. That is,the loss of one energy storage device will not significantly degrade theelectrical performance.

In some embodiments, placing the at least one energy storage layerbetween the stress carrying layers can involve a filament windingprocess. Such processes can involve winding the energy storage layerover a male mould and are known to one having ordinary skill in the art.Filament winding can be used to form energy storage assemblies having atubular structure such as, for example, a pipe.

In some embodiments, the energy storage devices of the present energystorage assemblies can contain carbon nanotubes. As noted previously,inclusion of carbon nanotubes in energy storage devices can enhancetheir electrical properties without increasing their weight. Theinclusion of carbon nanotubes in the energy storage devices can allow agreater energy density per unit weight to be realized. For example,replacement of carbon black in a traditional lithium-ion battery withcarbon nanotubes can allow approximately a 15-25 percent increase inpower density to be realized. Replacement of metal electrodes in anenergy storage device with carbon nanotube composite materials can allowstill greater increases in power density to be attained. By replacementof metal electrodes with carbon nanotube composite materials,significant reductions in weight can also be realized, since electrodematerials in traditional batteries and capacitors can make up to about60% of the gross weight of the cell.

Illustrative but non-limiting examples of carbon nanotube-enhancedenergy storage devices include those described in commonly assigned,co-pending U.S. patent application Ser. Nos. 13/039,025 and 13/039,028,each filed on Mar. 2, 2011, and Ser. No. 13/117,071, filed on May 26,2011, each of which is incorporated herein by reference in its entirety.When incorporated in an energy storage device, the carbon nanotubes canreplace any part of the energy storage device. Specifically, the carbonnanotubes can replace activated carbon or electrode materials, in someembodiments. In other embodiments, energy storage devices containingcarbon nanotubes that incorporate more non-traditional design paradigmscan also be used in the energy storage assemblies of the presentdisclosure. Further disclosure concerning supercapacitors containingcarbon nanotubes is set forth below.

When used in an energy storage device, carbon nanotubes can be employedin any suitable form. In some embodiments, the carbon nanotubes can bedispersed as individual carbon nanotubes. In some embodiments, thecarbon nanotubes can be incorporated in the energy storage device in theform of carbon nanotube-infused fibers. Such carbon nanotube-infusedfibers are described in commonly assigned, co-pending U.S. patentapplication Ser. Nos. 12/611,073, 12/611,101, and 12/611,103, all filedon Nov. 2, 2009, and Ser. No. 12/938,328, filed on Nov. 2, 2010, each ofwhich is incorporated herein by reference in its entirety. The fibermaterial of such carbon nanotube-infused fibers can generally varywithout limitation and can include, for example, glass fibers, carbonfibers, metal fibers, ceramic fibers, and organic fibers (e.g., aramidfibers) for example. Such carbon nanotube-infused fibers can be readilyprepared in spoolable lengths from commercially available continuousfibers or continuous fiber forms (e.g., fiber tows or fiber tapes). Inaddition, the carbon nanotubes' lengths, diameters, and coverage densitycan readily be varied by the above-referenced methods.

Depending on their growth conditions and subsequent processing, thecarbon nanotubes of the carbon nanotube-infused fibers can also beoriented such that they are substantially perpendicular to the surfaceof the fiber material or such that they are substantially parallel tothe longitudinal axis of the fiber material. In the present embodiments,by using carbon nanotube-infused fibers having substantiallyperpendicular carbon nanotubes, a better presentation of the carbonnanotube surface area can be realized (e.g., to an electrolyte). This isparticularly true when the carbon nanotubes are present in asubstantially unbundled state. The above-referenced methods forpreparing carbon nanotube-infused fibers are particularly adept atachieving a substantially perpendicular orientation and a substantiallyunbundled state, thereby providing carbon nanotube-infused fibers havinga high effective surface area for use in the present embodiments.Additional details concerning the carbon nanotube-infused fibers andmethods for production thereof are set forth hereinafter.

The types of carbon nanotubes infused to the continuous fibers cangenerally vary without limitation. In various embodiments, the carbonnanotubes infused to the continuous fibers can be, for example, any of anumber of cylindrically-shaped carbon allotropes of the fullerene familyincluding single-wall carbon nanotubes, double-wall carbon nanotubes,multi-wall carbon nanotubes, and any combination thereof. In someembodiments, the carbon nanotubes can be capped with a fullerene-likestructure. Stated another way, the carbon nanotubes have closed ends insuch embodiments. However, in other embodiments, the carbon nanotubescan remain open-ended. In some embodiments, closed carbon nanotube endscan be opened through treatment with an appropriate oxidizing agent(e.g., HNO₃/H₂SO₄). In some embodiments, the carbon nanotubes canencapsulate other materials. In some embodiments, the carbon nanotubescan be covalently functionalized after becoming infused to the fibermaterial. In some embodiments, a plasma process can be used to promotefunctionalization of the carbon nanotubes. In some embodiments, thecarbon nanotubes can be at least partially coated with another materialwhen infused to the continuous fibers.

Carbon nanotubes can be metallic, semimetallic or semiconductingdepending on their chirality. An established system of nomenclature fordesignating a carbon nanotube's chirality is recognized by one havingordinary skill in the art and is distinguished by a double index (n,m),where n and m are integers that describe the cut and wrapping ofhexagonal graphite when formed into a tubular structure. In addition tochirality, a carbon nanotube's diameter also influences its electricalconductivity and the related property of thermal conductivity. In thesynthesis of carbon nanotubes, the carbon nanotubes' diameters can becontrolled by using catalytic nanoparticles of a given size. Typically,a carbon nanotube's diameter is approximately that of the catalyticnanoparticle that catalyzes its formation. Therefore, carbon nanotubes'properties can be controlled in one respect by adjusting the size of thecatalytic nanoparticles used in their synthesis, for example. By way ofnon-limiting example, catalytic nanoparticles having a diameter of about1 nm can be used to infuse a fiber material with single-wall carbonnanotubes. Larger catalytic nanoparticles can be used to preparepredominantly multi-wall carbon nanotubes, which have larger diametersbecause of their multiple nanotube layers, or mixtures of single-walland multi-wall carbon nanotubes. Multi-wall carbon nanotubes typicallyhave a more complex conductivity profile than do single-wall carbonnanotubes due to interwall reactions that can occur between theindividual nanotube layers and redistribute current non-uniformly. Bycontrast, there is no change in current across different portions of asingle-wall carbon nanotube.

In general, the carbon nanotubes infused to the continuous fibers can beof any length. Longer carbon nanotubes are generally more advantageousin the present embodiments, since they can have a higher effectivesurface area. In various embodiments, the carbon nanotubes can have alength ranging between about 1 μm and about 1000 μm or between about 1μm and about 500 μm. In some embodiments, the carbon nanotubes can havea length ranging between about 100 μm and about 500 μm. In otherembodiments, the carbon nanotubes can have a length ranging betweenabout 1 μm and about 50 μm or between about 10 μm and about 25 μm. Insome embodiments, the carbon nanotubes can be substantially uniform inlength.

In some embodiments, an average length of the carbon nanotubes can rangebetween about 1 μm and about 500 μm, including about 1 μm, about 2 μm,about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm,about 9 μm, about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 60 μm,about 70 μm, about 80 μm, about 90 μm, about 100 μm, about 150 μm, about200 μm, about 250 μm, about 300 μm, about 350 μm, about 400 μm, about450 μm, about 500 μm, and all values and subranges therebetween. In someembodiments, an average length of the carbon nanotubes can be less thanabout 1 μm, including about 0.5 μm, for example, and all values andsubranges therebetween. In some embodiments, an average length of thecarbon nanotubes can range between about 1 μm and about 10 μm,including, for example, about 1 μm, about 2 μm, about 3 μm, about 4 μm,about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm,and all values and subranges therebetween. In still other embodiments,an average length of the carbon nanotubes can be greater than about 500μm, including, for example, about 510 μm, about 520 μm, about 550 μm,about 600 μm, about 700 μm, and all values and subranges therebetween.

The average length of the carbon nanotubes can be one factor thatdetermines the weight percentage of carbon nanotubes infused to thecontinuous fiber. In general, the carbon nanotube-infused fibersdescribed in the above-referenced, co-pending patent applications havemuch higher carbon nanotube loading percentages than can be obtained byother methods. For example, carbon nanotube-infused fibers can containbetween about 1% to about 30% or even about 40% to about 50% infusedcarbon nanotubes by weight. In the present embodiments, the chosencarbon nanotube weight percentage can be dictated by a desiredelectrical property (e.g., a desired capacitance for a supercapacitor).

The carbon nanotube coverage density on the continuous fibers can beanother factor that determines the weight percentage of infused carbonnanotubes. In some embodiments, the carbon nanotubes infused to thefiber material are generally uniform in density distribution, referringto the uniformity of the carbon nanotube density that is infused to thefiber material. As defined above, the tolerance for a uniform densitydistribution is plus or minus about 10% over the fiber material surfacearea that is infused with carbon nanotubes. By way of non-limitingexample, this tolerance is equivalent to about ±1500 carbonnanotubes/μm² for a carbon nanotube having a diameter of 8 nm and 5walls. Such a figure assumes that the space inside the carbon nanotubeis fillable. In some embodiments, the maximum carbon nanotube density,expressed as a percent coverage of the fiber material (i.e., thepercentage of the fiber material surface area that is covered withcarbon nanotubes) can be as high as about 55%, again assuming a carbonnanotube having an 8 nm diameter, 5 walls and fillable space within. 55%surface area coverage is equivalent to about 15,000 carbon nanotubes/μm²for a carbon nanotube having the referenced dimensions. In someembodiments, the density of coverage is up to about 15,000 carbonnanotubes/μm². One of ordinary skill in the art will recognize that awide range of carbon nanotube density distributions can be attained byvarying the disposition of the catalytic nanoparticles on the surface ofthe fiber material, the exposure time of the fiber material to carbonnanotube growth conditions, and the actual growth conditions themselvesused to infuse the carbon nanotubes to the fiber material.

In some embodiments, the carbon nanotubes grown on a fiber material canbe present as individual carbon nanotubes. That is, the carbon nanotubescan be present in a substantially non-bundled state. In someembodiments, the carbon nanotubes grown on the fiber material can bepresent as a carbon nanostructure containing interlinked carbonnanotubes. In such embodiments, substantially non-bundled carbonnanotubes can be present as an interlinked network of carbon nanotubes.In some embodiments, the interlinked network can contain carbonnanotubes that branch in a dendrimeric fashion from other carbonnanotubes. In some embodiments, the interlinked network can also containcarbon nanotubes that bridge between carbon nanotubes. In someembodiments, the interlinked network can also contain carbon nanotubesthat have a least a portion of their sidewalls shared with other carbonnanotubes.

In some embodiments, graphene or other carbon nanomaterials can be grownon a fiber material by appropriate modifications to the growthconditions. Such modifications will be evident to one having ordinaryskill in the art. It should be recognized that any embodiment hereinreferencing carbon nanotubes can also utilize graphene or other carbonnanomaterials while still residing within the spirit and scope of thepresent disclosure.

In various embodiments, individual continuous fibers (i.e., individualfilaments) can have a diameter ranging between about 1 μm and about 100μm. Continuous length fibers having diameters in this range are readilyavailable from a variety of commercial sources.

In general, the continuous fibers are used in a higher order fiber formin the present embodiments, rather than being used as individualfilaments. Such higher order fiber forms vary widely in structure andare considered in further detail immediately hereinafter. In someembodiments, the fiber form of the continuous fibers can be, forexample, a fiber tow, a fiber tape, and/or a fiber ribbon. In otherembodiments, the fiber form can be, for example, a fiber roving, a yarn,a fiber braid, a woven or non-woven fabric, a fiber ply, and/or a fibermat.

Rovings include soft strands of continuous fiber that have been twisted,attenuated and freed of foreign matter.

Fiber tows are generally compactly associated bundles of continuousfibers, which can be twisted together to give yarns in some embodiments.Yarns include closely associated bundles of twisted fibers, wherein eachfiber diameter in the yarn is relatively uniform. Yarns have varyingweights described by their ‘tex,’ (expressed as weight in grams per 1000linear meters), or ‘denier’ (expressed as weight in pounds per 10,000yards). For yarns, a typical tex range is usually between about 200 andabout 2000.

Fiber braids are rope-like structures of densely packed continuousfibers. Such rope-like structures can be assembled from yarns, forexample. Braided structures can optionally include a hollow portion.Alternately, a braided structure can be assembled about another corematerial.

Fiber tows can also include associated bundles of untwisted continuousfibers. Thus, fiber tows are a convenient form for manipulating largequantities of substantially parallel fibers in a single operation. As inyarns, the individual fiber diameters in a fiber tow are generallyuniform. Fiber tows also have varying weights and a tex range that isusually between about 200 and 2000. In addition, fiber tows arefrequently characterized by the number of thousands of individual fibersin the fiber tow, such as, for example, a 12K tow, a 24K tow, a 48K tow,and the like.

Tapes and ribbons contain continuous fibers that can be assembled asweaves or as non-woven flattened fiber tows, for example. Tapes can varyin width and are generally two-sided structures similar to a ribbon. Ina tape or ribbon, carbon nanotubes can be infused on one or both sidesthereof. Further, carbon nanotubes of different types, diameters orlengths can be grown on each side of a tape or a ribbon.

In some embodiments, the continuous fibers can be organized into fabricor sheet-like structures. These include, for example, woven fabrics,non-woven fabrics, non-woven fiber mats and fiber plies, in addition tothe tapes described above. Such higher ordered structures can beassembled from parent continuous fibers, fiber tows, yarns, or the like.

In supercapacitors containing carbon nanotube-infused fibers, thecapacitance is generally at least about 1 Farad/gram of continuousfibers. In some embodiments, the capacitance can range between about 1Farad/gram and about 100 Farad/gram of continuous fibers. In otherembodiments, the capacitance can range between about 1 Farad/gram andabout 50 Farad/gram of continuous fibers or between about 1 Farad/gramand about 40 Farad/gram of continuous fibers, including all subrangestherebetween.

According to more particular embodiments described herein, the infusedcarbon nanotubes of an energy storage device can be at least partiallycovered with a coating. When used in a supercapacitor, such a coatingcan increase the supercapacitor's capacitance. In certain instances, theincrease in capacitance can be an order of magnitude or more (e.g., atleast about 10-fold greater) relative to a like supercapacitor lackingthe coating on the infused carbon nanotubes. In such embodiments, thecapacitance can be at least about 10 Farad/gram of continuous fibers. Insome embodiments, supercapacitors having coated carbon nanotubes canhave a capacitance ranging between about 10 Farad/gram and about 100Farad/gram of continuous fibers.

Suitable materials for coating carbon nanotubes in order to increasecapacitance of a supercapacitor can include, for example, conductingpolymers, main group metal compounds, transition metal compounds, andcombinations thereof. In some embodiments, the carbon nanotubes can becompletely coated with the coating material. In other embodiments, thecarbon nanotubes can be partially coated with the coating material. Insome embodiments, a portion of the carbon nanotubes can be completelycoated with the coating material and another portion of the carbonnanotubes can remain partially coated or uncoated. In some embodiments,carbon nanotube coatings can include materials such as, for example,polypyrrole, MnO₂, RuO₂, or various combinations thereof.

When used, the carbon nanotube coating can generally be present in anamount ranging between about 1 percent and about 90 percent by weight ofthe carbon nanotube-infused fibers. In more particular embodiments, anamount of the carbon nanotube coating can range between about 2.5percent and about 70 percent, or between about 5 percent and about 50percent by weight of the carbon nanotube-infused fibers.

When used, a thickness of the carbon nanotube coating can generallyrange between about 0.0001 microns and about 10 microns. In moreparticular embodiments, a thickness of the carbon nanotube coating canrange between about 0.001 microns and 1 microns, or between about 0.005microns and about 0.5 microns.

Embodiments disclosed herein utilize carbon nanotube-infused fibers thatcan be readily prepared by methods described in commonly-owned,co-pending U.S. patent application Ser. Nos. 12/611,073, 12/611,101,12/611,103, and 12/938,328 each of which is incorporated by referenceherein in its entirety. A brief description of the processes describedtherein follows.

To infuse carbon nanotubes to a fiber material, the carbon nanotubes aresynthesized directly on the fiber material. In some embodiments, this isaccomplished by first disposing a carbon nanotube-forming catalyst(e.g., catalytic nanoparticles) on the fiber material. A number ofpreparatory processes can be performed prior to this catalystdeposition.

In some embodiments, the fiber material can be optionally treated with aplasma to prepare the fiber surface to accept the catalyst. For example,a plasma treated glass fiber material can provide a roughened glassfiber surface in which the carbon nanotube-forming catalyst can bedeposited. In some embodiments, the plasma also serves to “clean” thefiber surface. The plasma process for “roughing” the fiber surface thusfacilitates catalyst deposition. The roughness is typically on the scaleof nanometers. In the plasma treatment process craters or depressionsare formed that are nanometers deep and nanometers in diameter. Suchsurface modification can be achieved using a plasma of any one or moreof a variety of different gases, including, without limitation, argon,helium, oxygen, ammonia, nitrogen and hydrogen. In addition, the plasmatreatment of the fiber surface can add functional groups thereto thatcan be useful in some embodiments.

In some embodiments, where a fiber material being employed has a sizingmaterial associated with it, such sizing can be optionally removed priorto catalyst deposition. Optionally, the sizing material can be removedafter catalyst deposition. In some embodiments, sizing material removalcan be accomplished during carbon nanotube synthesis or just prior tocarbon nanotube synthesis in a pre-heat step. In other embodiments, somesizing materials can remain throughout the entire carbon nanotubesynthesis process.

Yet another optional step prior to or concomitant with deposition of thecarbon nanotube-forming catalyst (i.e., catalytic nanoparticles) isapplication of a barrier coating on the fiber material. Barrier coatingsare materials designed to protect the integrity of sensitive fibermaterials, such as carbon fibers, organic fibers, glass fibers, metalfibers, and the like. Such a barrier coating can include, for example,an alkoxysilane, an alumoxane, alumina nanoparticles, spin on glass andglass nanoparticles. For example, in an embodiment the barrier coatingis Accuglass T-11 Spin-On Glass (Honeywell International Inc.,Morristown, N.J.). The carbon nanotube-forming catalyst can be added tothe uncured barrier coating material and then applied to the fibermaterial together, in one embodiment. In other embodiments, the barriercoating material can be added to the fiber material prior to depositionof the carbon nanotube-forming catalyst. In such embodiments, thebarrier coating can be partially cured prior to catalyst deposition. Thebarrier coating material can be of a sufficiently thin thickness toallow exposure of the carbon nanotube-forming catalyst to the carbonfeedstock gas for subsequent CVD- or like carbon nanotube growth. Insome embodiments, the barrier coating thickness is less than or aboutequal to the effective diameter of the carbon nanotube-forming catalyst.Once the carbon nanotube-forming catalyst and the barrier coating are inplace, the barrier coating can be fully cured. In some embodiments, thethickness of the barrier coating can be greater than the effectivediameter of the carbon nanotube-forming catalyst so long as it stillpermits access of carbon nanotube feedstock gases to the sites of thecatalyst. Such barrier coatings can be sufficiently porous to allowaccess of carbon feedstock gases to the carbon nanotube-formingcatalyst.

In some embodiments, the thickness of the barrier coating ranges betweenabout 10 nm and about 100 nm. In other embodiments, the thickness of thebarrier coating ranges between about 10 nm and about 50 nm, including 40nm. In some embodiments, the thickness of the barrier coating is lessthan about 10 nm, including about 1 nm, about 2 nm, about 3 nm, about 4nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, andabout 10 nm, including all values and subranges therebetween.

Without being bound by theory, the barrier coating can serve as anintermediate layer between the fiber material and the carbon nanotubesand mechanically infuses the carbon nanotubes to the fiber material.Such mechanical infusion via a barrier coating provides a robust systemfor carbon nanotube growth in which the fiber material serves as aplatform for organizing the carbon nanotubes, while still allowing thebeneficial carbon nanotube properties to be conveyed to the fibermaterial. Moreover, benefits of including a barrier coating can include,for example, protection of the fiber material from chemical damage dueto moisture exposure and/or thermal damage at the elevated temperaturesused to promote carbon nanotube growth.

As described further below, the carbon nanotube-forming catalyst can beprepared as a liquid solution that contains the carbon nanotube-formingcatalyst as transition metal catalytic nanoparticles. The diameters ofthe synthesized carbon nanotubes are related to the size of thetransition metal catalytic nanoparticles as described above.

Carbon nanotube synthesis can be based on a chemical vapor deposition(CVD) process or related carbon nanotube growth process which occurs atelevated temperatures. In some embodiments, the CVD-based growth processcan be plasma-enhanced by providing an electric field during the growthprocess such that the carbon nanotube growth follows the direction ofthe electric field. Other illustrative carbon nanotube growth processesinclude, for example, micro-cavity, laser ablation, flame synthesis, arcdischarge, and high pressure carbon monoxide (HiPCO) synthesis. Thespecific temperature is a function of catalyst choice, but can typicallybe in a range of about 500° C. to about 1000° C. Accordingly, carbonnanotube synthesis involves heating the fiber material to a temperaturein the aforementioned range to support carbon nanotube growth.

In some embodiments, CVD-promoted carbon nanotube growth on thecatalyst-laden fiber material is performed. The CVD process can bepromoted by, for example, a carbon-containing feedstock gas such asacetylene, ethylene, and/or methane. The carbon nanotube growthprocesses also generally use an inert gas (e.g., nitrogen, argon, and/orhelium) as a primary carrier gas. The carbon-containing feedstock gas istypically provided in a range from between about 0% to about 15% of thetotal mixture. A substantially inert environment for CVD growth can beprepared by removal of moisture and oxygen from the growth chamber.

In the carbon nanotube growth process, carbon nanotubes grow at thesites of transition metal catalytic nanoparticles that are operable forcarbon nanotube growth. The presence of a strong plasma-creatingelectric field can be optionally employed to affect carbon nanotubegrowth. That is, the growth tends to follow the direction of theelectric field. By properly adjusting the geometry of the plasma sprayand electric field, vertically aligned carbon nanotubes (i.e.,perpendicular to the surface of the fiber material) can be synthesized.Under certain conditions, even in the absence of a plasma,closely-spaced carbon nanotubes can maintain a substantially verticalgrowth direction resulting in a dense array of carbon nanotubesresembling a carpet or forest. In some embodiments, an interlinkedcarbon nanotube network can be produced.

Returning to the catalyst deposition process, a carbon nanotube-formingcatalyst is deposited to provide a layer (typically no more than amonolayer) of catalytic nanoparticles on the fiber material for thepurpose of growing carbon nanotubes thereon. The operation of depositingcatalytic nanoparticles on the fiber material can be accomplished by anumber of techniques including, for example, spraying or dip coating asolution of catalytic nanoparticles or by gas phase deposition, whichcan occur by a plasma process. Thus, in some embodiments, after forminga catalyst solution in a solvent, the catalyst can be applied byspraying or dip coating the fiber material with the solution, orcombinations of spraying and dip coating. Either technique, used aloneor in combination, can be employed once, twice, thrice, four times, upto any number of times to provide a fiber material that is sufficientlyuniformly coated with catalytic nanoparticles that are operable forformation of carbon nanotubes. When dip coating is employed, forexample, a fiber material can be placed in a first dip bath for a firstresidence time in the first dip bath. When employing a second dip bath,the fiber material can be placed in the second dip bath for a secondresidence time. For example, fiber materials can be subjected to asolution of carbon nanotube-forming catalyst for between about 3 secondsto about 90 seconds depending on the dip configuration and linespeed.Employing spraying or dip coating processes, a fiber material with acatalyst surface density of less than about 5% surface coverage to ashigh as about 80% surface coverage can be obtained. At higher surfacedensities (e.g., about 80%), the carbon nanotube-forming catalystnanoparticles are nearly a monolayer. In some embodiments, the processof coating the carbon nanotube-forming catalyst on the fiber materialproduces no more than a monolayer. For example, carbon nanotube growthon a stack of carbon nanotube-forming catalyst can erode the degree ofinfusion of the carbon nanotubes to the fiber material. In otherembodiments, transition metal catalytic nanoparticles can be depositedon the fiber material using evaporation techniques, electrolyticdeposition techniques, and other processes known to those of ordinaryskill in the art, such as addition of the transition metal catalyst to aplasma feedstock gas as a metal organic, metal salt or other compositionpromoting gas phase transport.

Because processes to manufacture carbon nanotube-infused fibers aredesigned to be continuous, a spoolable fiber material can be dip-coatedin a series of baths where dip coating baths are spatially separated. Ina continuous process in which nascent fibers are being generated denovo, such as newly formed glass fibers from a furnace, dip bath orspraying of a carbon nanotube-forming catalyst can be the first stepafter sufficiently cooling the newly formed fiber material. In someembodiments, cooling of newly formed glass fibers can be accomplishedwith a cooling jet of water which has the carbon nanotube-formingcatalyst particles dispersed therein.

In some embodiments, application of a carbon nanotube-forming catalystcan be performed in lieu of application of a sizing when generating afiber and infusing it with carbon nanotubes in a continuous process. Inother embodiments, the carbon nanotube-forming catalyst can be appliedto newly formed fiber materials in the presence of other sizing agents.Such simultaneous application of a carbon nanotube-forming catalyst andother sizing agents can provide the carbon nanotube-forming catalyst insurface contact with the fiber material to insure carbon nanotubeinfusion. In yet further embodiments, the carbon nanotube-formingcatalyst can be applied to nascent fibers by spray or dip coating whilethe fiber material is in a sufficiently softened state, for example,near or below the annealing temperature, such that the carbonnanotube-forming catalyst is slightly embedded in the surface of thefiber material. When depositing the carbon nanotube-forming catalyst onhot glass fiber materials, for example, care should be given to notexceed the melting point of the carbon nanotube-forming catalyst,thereby causing nanoparticle fusion and loss of control of the carbonnanotube characteristics (e.g., diameter) as a result.

Carbon nanotubes infused to a fiber material can serve to protect thefiber material from conditions including, for example, moisture,oxidation, abrasion, compression and/or other environmental conditions.In this case, the carbon nanotubes themselves can act as a sizing agent.Such a carbon nanotube-based sizing agent can be applied to a fibermaterial in lieu of or in addition to conventional sizing agents. Whenpresent, conventional sizing agents can be applied before or after theinfusion and growth of carbon nanotubes on the fiber material.Conventional sizing agents vary widely in type and function and include,for example, surfactants, anti-static agents, lubricants, siloxanes,alkoxysilanes, aminosilanes, silanes, silanols, polyvinyl alcohol,starch, and mixtures thereof. Such conventional sizing agents can beused to protect the carbon nanotubes themselves from various conditionsor to convey further properties to the fiber material that are notimparted by the carbon nanotubes. In some embodiments, a conventionalsizing agent can be removed from the fiber material prior to carbonnanotube growth. Optionally, a conventional sizing agent can be replacedwith another conventional sizing agent that is more compatible with thecarbon nanotubes or the carbon nanotube growth conditions.

The carbon nanotube-forming catalyst solution can be a transition metalnanoparticle solution of any d-block transition metal. In addition, thenanoparticles can include alloys and non-alloy mixtures of d-blockmetals in elemental form, in salt form, and mixtures thereof. Such saltforms include, without limitation, oxides, carbides, nitrides, nitrates,sulfides, sulfates, phosphates, halides (e.g., fluorides, chlorides,bromides, and iodides), acetates, citrates and the like. Non-limitingillustrative transition metal nanoparticles include, for example, Ni,Fe, Co, Mo, Cu, Pt, Au, and Ag, salts thereof and mixtures thereof. Manytransition metal nanoparticle catalysts are readily commerciallyavailable from a variety of suppliers, including, for example, FerrotecCorporation (Bedford, N.H.).

Catalyst solutions used for applying the carbon nanotube-formingcatalyst to the fiber material can be in any common solvent that allowsthe carbon nanotube-forming catalyst to be uniformly dispersedthroughout. Such solvents can include, without limitation, water,acetone, hexane, isopropyl alcohol, toluene, ethanol, methanol,tetrahydrofuran (THF), cyclohexane or any other solvent with controlledpolarity to create an appropriate dispersion of the carbonnanotube-forming catalytic nanoparticles therein. Concentrations ofcarbon nanotube-forming catalyst in the catalyst solution can be in arange from about 1:1 to about 1:10,000 catalyst to solvent.

In some embodiments, after applying the carbon nanotube-forming catalystto the fiber material, the fiber material can be optionally heated to asoftening temperature. This step can aid in embedding the carbonnanotube-forming catalyst in the surface of the fiber material toencourage seeded growth and prevent tip growth where the catalyst floatsat the tip of the leading edge a growing carbon nanotube. In someembodiments heating of the fiber material after disposing the carbonnanotube-forming catalyst on the fiber material can be at a temperaturebetween about 500° C. and about 1000° C. Heating to such temperatures,which can be used for carbon nanotube growth, can serve to remove anypre-existing sizing agents on the fiber material allowing deposition ofthe carbon nanotube-forming catalyst directly on the fiber material. Insome embodiments, the carbon nanotube-forming catalyst can also beplaced on the surface of a sizing coating prior to heating. The heatingstep can be used to remove sizing material while leaving the carbonnanotube-forming catalyst disposed on the surface of the fiber material.Heating at these temperatures can be performed prior to or substantiallysimultaneously with introduction of a carbon-containing feedstock gasfor carbon nanotube growth.

In some embodiments, the process of infusing carbon nanotubes to a fibermaterial can include removing sizing agents from the fiber material,applying a carbon nanotube-forming catalyst to the fiber material aftersizing removal, heating the fiber material to at least about 500° C.,and synthesizing carbon nanotubes on the fiber material. In someembodiments, operations of the carbon nanotube infusion process caninclude removing sizing from a fiber material, applying a carbonnanotube-forming catalyst to the fiber material, heating the fibermaterial to a temperature operable for carbon nanotube synthesis andspraying a carbon plasma onto the catalyst-laden fiber material. Thus,where commercial fiber materials are employed, processes forconstructing carbon nanotube-infused fibers can include a discrete stepof removing sizing from the fiber material before disposing thecatalytic nanoparticles on the fiber material. Some commercial sizingmaterials, if present, can prevent surface contact of the carbonnanotube-forming catalyst with the fiber material and inhibit carbonnanotube infusion to the fiber material. In some embodiments, wheresizing removal is assured under carbon nanotube growth conditions,sizing removal can be performed after deposition of the carbonnanotube-forming catalyst but just prior to or during providing acarbon-containing feedstock gas.

The step of synthesizing carbon nanotubes can include numeroustechniques for forming carbon nanotubes, including, without limitation,micro-cavity, thermal or plasma-enhanced CVD techniques, laser ablation,arc discharge, flame synthesis, and high pressure carbon monoxide(HiPCO). During CVD, in particular, a sized fiber material with carbonnanotube-forming catalyst disposed thereon, can be used directly. Insome embodiments, any conventional sizing agents can be removed duringcarbon nanotube synthesis. In some embodiments other sizing agents arenot removed, but do not hinder carbon nanotube synthesis and infusion tothe fiber material due to the diffusion of the carbon-containingfeedstock gas through the sizing. In some embodiments, acetylene gas canbe ionized to create a jet of cold carbon plasma for carbon nanotubesynthesis. The plasma is directed toward the catalyst-laden fibermaterial. Thus, in some embodiments synthesizing carbon nanotubes on afiber material can include (a) forming a carbon plasma; and (b)directing the carbon plasma onto the catalyst disposed on the fibermaterial. The diameters of the carbon nanotubes that are grown aredictated by the size of the carbon nanotube-forming catalyst. In someembodiments, a sized fiber material can be heated to between about 550°C. and about 800° C. to facilitate carbon nanotube growth. To initiatethe growth of carbon nanotubes, two or more gases are bled into thereactor: an inert carrier gas (e.g., argon, helium, or nitrogen) and acarbon-containing feedstock gas (e.g., acetylene, ethylene, ethanol ormethane). Carbon nanotubes grow at the sites of the carbonnanotube-forming catalyst.

In some embodiments, a CVD growth process can be plasma-enhanced. Aplasma can be generated by providing an electric field during the growthprocess. Carbon nanotubes grown under these conditions can follow thedirection of the electric field. Thus, by adjusting the geometry of thereactor, vertically aligned carbon nanotubes can be grown where thecarbon nanotubes are substantially perpendicular to the surface of thefiber material (i.e., radial growth). In some embodiments, a plasma isnot required for radial growth to occur about the fiber material. Forfiber materials that have distinct sides such as, for example, tapes,mats, fabrics, plies, and the like, the carbon nanotube-forming catalystcan be disposed on one or both sides of the fiber material.Correspondingly, under such conditions, carbon nanotubes can be grown onone or both sides of the fiber material as well.

As described above, the carbon nanotube synthesis is performed at a ratesufficient to provide a continuous process for infusing spoolable lengthfiber materials with carbon nanotubes. Numerous apparatus configurationsfacilitate such a continuous synthesis as exemplified below.

In some embodiments, carbon nanotube-infused fiber materials can beprepared in an “all-plasma” process. In such embodiments, the fibermaterials pass through numerous plasma-mediated steps to form the finalcarbon nanotube-infused fiber materials. The first of the plasmaprocesses, can include a step of fiber surface modification. This is aplasma process for “roughing” the surface of the fiber material tofacilitate catalyst deposition, as described above. Optionally, afunctionalization of the fiber material can also be involved. As alsodescribed above, surface modification can be achieved using a plasma ofany one or more of a variety of different gases, including, withoutlimitation, argon, helium, oxygen, ammonia, hydrogen, and nitrogen.

After surface modification, the fiber material proceeds to catalystapplication. In the present all-plasma process, this step is a plasmaprocess for depositing the carbon nanotube-forming catalyst on the fibermaterial. The carbon nanotube-forming catalyst is typically a transitionmetal as described above. The transition metal catalyst can be added toa plasma feedstock gas as a precursor in non-limiting forms including,for example, a ferrofluid, a metal organic, a metal salt, mixturesthereof or any other composition suitable for promoting gas phasetransport. The carbon nanotube-forming catalyst can be applied at roomtemperature in ambient environment with neither vacuum nor an inertatmosphere being required. In some embodiments, the fiber material canbe cooled prior to catalyst application.

Continuing the all-plasma process, carbon nanotube synthesis occurs in acarbon nanotube-growth reactor. Carbon nanotube growth can be achievedthrough the use of plasma-enhanced chemical vapor deposition, whereincarbon plasma is sprayed onto the catalyst-laden fibers. Since carbonnanotube growth occurs at elevated temperatures (typically in a range ofabout 500° C. to about 1000° C. depending on the catalyst), thecatalyst-laden fibers can be heated prior to being exposed to the carbonplasma. For the carbon nanotube infusion process, the fiber material canbe optionally heated until softening occurs. After heating, the fibermaterial is ready to receive the carbon plasma. The carbon plasma can begenerated, for example, by passing a carbon-containing feedstock gassuch as, for example, acetylene, ethylene, ethanol, and the like,through an electric field that is capable of ionizing the gas. This coldcarbon plasma is directed, via spray nozzles, to the fiber material. Thefiber material can be in close proximity to the spray nozzles, such aswithin about 1 centimeter of the spray nozzles, to receive the plasma.In some embodiments, heaters can be disposed above the fiber material atthe plasma sprayers to maintain the elevated temperature of the fibermaterial.

Another configuration for continuous carbon nanotube synthesis involvesa special rectangular reactor for the synthesis and growth of carbonnanotubes directly on fiber materials. The reactor can be designed foruse in a continuous in-line process for producing carbonnanotube-infused fiber materials. In some embodiments, carbon nanotubesare grown via a CVD process at atmospheric pressure and an elevatedtemperature in the range of about 550° C. and about 800° C. in amulti-zone reactor. The fact that the carbon nanotube synthesis occursat atmospheric pressure is one factor that facilitates the incorporationof the reactor into a continuous processing line for carbon nanotubeinfusion to the fiber materials. Another advantage consistent within-line continuous processing using such a zone reactor is that carbonnanotube growth occurs in seconds, as opposed to minutes (or longer), asin other procedures and apparatus configurations typical in the art.

Carbon nanotube synthesis reactors in accordance with the variousembodiments include the following features:

Rectangular Configured Synthesis Reactors:

The cross-section of a typical carbon nanotube synthesis reactor knownin the art is circular. There are a number of reasons for thisincluding, for example, historical reasons (e.g., cylindrical reactorsare often used in laboratories) and convenience (e.g., flow dynamics areeasy to model in cylindrical reactors, heater systems readily acceptcircular tubes (e.g., quartz, etc.), and ease of manufacturing.Departing from the cylindrical convention, the present disclosureprovides a carbon nanotube synthesis reactor having a rectangular crosssection. The reasons for the departure include at least the following:

1) Inefficient Use of Reactor Volume. Since many fiber materials thatcan be processed by the reactor are relatively planar (e.g., flat tapes,sheet-like forms, or spread tows or rovings), a circular cross-sectionis an inefficient use of the reactor volume. This inefficiency resultsin several drawbacks for cylindrical carbon nanotube synthesis reactorsincluding, for example, a) maintaining a sufficient system purge;increased reactor volume requires increased gas flow rates to maintainthe same level of gas purge, resulting in inefficiencies for high volumeproduction of carbon nanotubes in an open environment; b) increasedcarbon-containing feedstock gas flow rates; the relative increase ininert gas flow for system purge, as per a) above, requires increasedcarbon-containing feedstock gas flow rates. Consider that the volume ofan illustrative 12K glass fiber roving is about 2000 times less than thetotal volume of a synthesis reactor having a rectangular cross-section.In an equivalent cylindrical reactor (i.e., a cylindrical reactor thathas a width that accommodates the same planarized glass fiber materialas the rectangular cross-section reactor), the volume of the glass fibermaterial is about 17,500 times less than the volume of the reactor.Although gas deposition processes, such as CVD, are typically governedby pressure and temperature alone, volume can have a significant impacton the efficiency of deposition. With a rectangular reactor there is astill excess volume, and this excess volume facilitates unwantedreactions. However, a cylindrical reactor has about eight times thatvolume available for facilitating unwanted reactions. Due to thisgreater opportunity for competing reactions to occur, the desiredreactions effectively occur more slowly in a cylindrical reactor. Such aslow down in carbon nanotube growth, is problematic for the developmentof continuous growth processes. Another benefit of a rectangular reactorconfiguration is that the reactor volume can be decreased further stillby using a small height for the rectangular chamber to make the volumeratio better and the reactions even more efficient. In some embodimentsdisclosed herein, the total volume of a rectangular synthesis reactor isno more than about 3000 times greater than the total volume of a fibermaterial being passed through the synthesis reactor. In some furtherembodiments, the total volume of the rectangular synthesis reactor is nomore than about 4000 times greater than the total volume of the fibermaterial being passed through the synthesis reactor. In some stillfurther embodiments, the total volume of the rectangular synthesisreactor is less than about 10,000 times greater than the total volume ofthe fiber material being passed through the synthesis reactor.Additionally, it is notable that when using a cylindrical reactor, morecarbon-containing feedstock gas is required to provide the same flowpercent as compared to reactors having a rectangular cross section. Itshould be appreciated that in some other embodiments, the synthesisreactor has a cross-section that is described by polygonal forms thatare not rectangular, but are relatively similar thereto and provide asimilar reduction in reactor volume relative to a reactor having acircular cross section; and c) problematic temperature distribution;when a relatively small-diameter reactor is used, the temperaturegradient from the center of the chamber to the walls thereof is minimal,but with increased reactor size, such as would be used forcommercial-scale production, such temperature gradients increase.Temperature gradients result in product quality variations across thefiber material (i.e., product quality varies as a function of radialposition). This problem is substantially avoided when using a reactorhaving a rectangular cross-section. In particular, when a planarsubstrate is used, reactor height can be maintained constant as the sizeof the substrate scales upward. Temperature gradients between the topand bottom of the reactor are essentially negligible and, as aconsequence, thermal issues and the product-quality variations thatresult are avoided.

2) Gas introduction. Because tubular furnaces are normally employed inthe art, typical carbon nanotube synthesis reactors introduce gas at oneend and draw it through the reactor to the other end. In someembodiments disclosed herein, gas can be introduced at the center of thereactor or within a target growth zone, symmetrically, either throughthe sides or through the top and bottom plates of the reactor. Thisimproves the overall carbon nanotube growth rate because the incomingfeedstock gas is continuously replenishing at the hottest portion of thesystem, which is where carbon nanotube growth is most active.

Zoning.

Chambers that provide a relatively cool purge zone extend from both endsof the rectangular synthesis reactor. Applicants have determined that ifa hot gas were to mix with the external environment (i.e., outside ofthe rectangular reactor), there would be increased degradation of thefiber material. The cool purge zones provide a buffer between theinternal system and external environments. Carbon nanotube synthesisreactor configurations known in the art typically require that thesubstrate is carefully (and slowly) cooled. The cool purge zone at theexit of the present rectangular carbon nanotube growth reactor achievesthe cooling in a short period of time, as required for continuousin-line processing.

Non-Contact, Hot-Walled, Metallic Reactor.

In some embodiments, a metallic hot-walled reactor (e.g., stainlesssteel) is employed. Use of this type of reactor can appearcounterintuitive because metal, and stainless steel in particular, ismore susceptible to carbon deposition (i.e., soot and by-productformation). Thus, most carbon nanotube synthesis reactors are made fromquartz because there is less carbon deposited, quartz is easier toclean, and quartz facilitates sample observation. However, Applicantshave observed that the increased soot and carbon deposition on stainlesssteel results in more consistent, efficient, faster, and stable carbonnanotube growth. Without being bound by theory it has been indicatedthat, in conjunction with atmospheric operation, the CVD processoccurring in the reactor is diffusion limited. That is, the carbonnanotube-forming catalyst is “overfed;” too much carbon is available inthe reactor system due to its relatively higher partial pressure (thanif the reactor was operating under partial vacuum). As a consequence, inan open system—especially a clean one—too much carbon can adhere to theparticles of carbon nanotube-forming catalyst, compromising theirability to synthesize carbon nanotubes. In some embodiments, therectangular reactor is intentionally run when the reactor is “dirty,”that is with soot deposited on the metallic reactor walls. Once carbondeposits to a monolayer on the walls of the reactor, carbon will readilydeposit over itself. Since some of the available carbon is “withdrawn”due to this mechanism, the remaining carbon feedstock, in the form ofradicals, reacts with the carbon nanotube-forming catalyst at a ratethat does not poison the catalyst. Existing systems run “cleanly” which,if they were open for continuous processing, would produce a much loweryield of carbon nanotubes at reduced growth rates.

Although it is generally beneficial to perform carbon nanotube synthesis“dirty” as described above, certain portions of the apparatus (e.g., gasmanifolds and inlets) can nonetheless negatively impact the carbonnanotube growth process when soot creates blockages. In order to combatthis problem, such areas of the carbon nanotube growth reaction chambercan be protected with soot inhibiting coatings such as, for example,silica, alumina, or MgO. In practice, these portions of the apparatuscan be dip-coated in these soot inhibiting coatings. Metals such asINVAR® can be used with these coatings as INVAR has a similar CTE(coefficient of thermal expansion) ensuring proper adhesion of thecoating at higher temperatures, preventing the soot from significantlybuilding up in critical zones.

Combined Catalyst Reduction and Carbon Nanotube Synthesis.

In the carbon nanotube synthesis reactor disclosed herein, both catalystreduction and carbon nanotube growth occur within the reactor. This issignificant because the reduction step cannot be accomplished timelyenough for use in a continuous process if performed as a discreteoperation. In a typical process known in the art, a reduction steptypically takes 1-12 hours to perform. Both operations occur in areactor in accordance with the present disclosure due, at least in part,to the fact that carbon-containing feedstock gas is introduced at thecenter of the reactor, not the end as would be typical in the art usingcylindrical reactors. The reduction process occurs as the fiber materialenters the heated zone. By this point, the gas has had time to reactwith the walls and cool off prior to reducing the catalyst (via hydrogenradical interactions). It is this transition region where the reductionoccurs. At the hottest isothermal zone in the system, carbon nanotubegrowth occurs, with the greatest growth rate occurring proximal to thegas inlets near the center of the reactor.

In some embodiments, when loosely affiliated fiber materials including,for example, tows or rovings are employed (e.g., a glass roving), thecontinuous process can include steps that spread out the strands and/orfilaments of the tow or roving. Thus, as a tow or roving is unspooled itcan be spread using a vacuum-based fiber spreading system, for example.When employing sized glass fiber rovings, for example, which can berelatively stiff, additional heating can be employed in order to“soften” the roving to facilitate fiber spreading. The spread fiberswhich contain individual filaments can be spread apart sufficiently toexpose an entire surface area of the filaments, thus allowing the rovingto more efficiently react in subsequent process steps. For example, aspread tow or roving can pass through a surface treatment step that iscomposed of a plasma system as described above. The roughened, spreadfibers then can pass through a carbon nanotube-forming catalyst dipbath. The result is fibers of the glass roving that have catalystparticles distributed radially on their surface. The catalyzed-ladenfibers of the roving then enter an appropriate carbon nanotube growthchamber, such as the rectangular chamber described above, where a flowthrough atmospheric pressure CVD or plasma enhanced-CVD process is usedto synthesize carbon nanotubes at rates as high as several microns persecond. The fibers of the roving, now having radially aligned carbonnanotubes, exit the carbon nanotube growth reactor.

It is understood that modifications which do not substantially affectthe activity of the various embodiments of this invention are alsoincluded within the definition of the invention provided herein.Although the invention has been described with reference to thedisclosed embodiments, those of ordinary skill in the art will readilyappreciate that these embodiments are only illustrative of theinvention. It should be understood that various modifications can bemade without departing from the spirit of the invention. The particularembodiments disclosed above are illustrative only, as the presentinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularillustrative embodiments disclosed above may be altered, combined, ormodified and all such variations are considered within the scope andspirit of the present invention. While compositions and methods aredescribed in terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and operations.All numbers and ranges disclosed above can vary by some amount. Whenevera numerical range with a lower limit and an upper limit is disclosed,any number and any subrange falling within the broader range isspecifically disclosed. Also, the terms in the claims have their plain,ordinary meaning unless otherwise explicitly and clearly defined by thepatentee. If there is any conflict in the usages of a word or term inthis specification and one or more patent or other documents that may beincorporated herein by reference, the definitions that are consistentwith this specification should be adopted.

What is claimed is the following:
 1. An energy storage assemblycomprising: at least one energy storage layer comprising: an insulatinglayer having a plurality of openings arranged in a spaced apart manner;a plurality of energy storage devices, each energy storage device beingcontained within one of said openings, wherein at least some of theenergy storage devices contain carbon nanotube-infused fibers; and asupport material upon which the plurality of energy storage devices isdisposed, wherein the plurality of energy storage devices areelectrically connected to one another through electrical connections onthe support material.
 2. The energy storage assembly of claim 1, whereinthe insulating layer is disposed on the support material.
 3. The energystorage assembly of claim 1, wherein at least some of the energy storagedevices are electrically connected to one another in parallel.
 4. Theenergy storage assembly of claim 3, wherein at least some of the energystorage devices are electrically connected to one another in series. 5.The energy storage assembly of claim 1, wherein the insulating layercomprises a material selected from the group consisting of a polymer anda fiber-reinforced polymer composite.
 6. The energy storage assembly ofclaim 1, wherein at least some of the energy storage devices comprisebatteries.
 7. The energy storage assembly of claim 1, wherein at leastsome of the energy storage devices comprise capacitors orsupercapacitors.
 8. The energy storage assembly of claim 1, wherein atleast some of the energy storage devices contain carbon nanotubes. 9.The energy storage assembly of claim 1, wherein carbon nanotubes of thecarbon-nanotube infused fibers are at least partially covered with acoating selected from the group consisting of polypyrrole, MnO₂, RuO₂,and combinations thereof.
 10. The energy storage assembly of claim 1,further comprising: at least one stress carrying layer in contact withthe at least one energy storage layer.
 11. The energy storage assemblyof claim 10, wherein the at least one energy storage layer is disposedbetween at least two stress carrying layers.
 12. The energy storageassembly of claim 11, wherein the at least two stress carrying layerseach comprise a fiber-reinforced polymer composite.
 13. The energystorage assembly of claim 1, wherein the plurality of energy storagedevices are arranged in a grid structure in the at least one energystorage layer.
 14. The energy storage assembly of claim 1, wherein aheight of the insulating layer is at least that of the energy storagedevices.
 15. An energy storage assembly comprising: at least two stresscarrying layers; and at least one energy storage layer disposed betweenthe at least two stress carrying layers, the at least one energy storagelayer comprising: a support material; an insulating layer having aplurality of openings arranged in a spaced apart manner; and a pluralityof energy storage devices disposed on the support material, theplurality of energy storage devices being electrically connected to oneanother through electrical connections on the support material, eachenergy storage device being contained within one of said openings,wherein at least some of the energy storage devices contain carbonnanotube-infused fibers.
 16. The energy storage assembly of claim 15,wherein the at least one energy storage layer comprises up to about 90%of a thickness of the energy storage assembly.
 17. The energy storageassembly of claim 15, wherein the insulating layer comprises a materialselected from the group consisting of a polymer and a fiber-reinforcedpolymer composite.
 18. The energy storage assembly of claim 15, whereineach energy storage device is enveloped with a casing; and wherein thecasing comprises the insulating layer.
 19. The energy storage assemblyof claim 15, wherein each of said openings comprise a hole in theinsulating layer.
 20. The energy storage assembly of claim 15, whereinat least some of the energy storage devices comprise batteries.
 21. Theenergy storage assembly of claim 15, wherein at least some of the energystorage devices comprise capacitors or supercapacitors.
 22. The energystorage assembly of claim 15, wherein at least some of the energystorage devices contain carbon nanotubes.
 23. The energy storageassembly of claim 15, wherein the plurality of energy storage devicesare arranged in a grid structure in the at least one energy storagelayer.
 24. The energy storage assembly of claim 1, wherein: the supportmaterial comprises a layer of material upon which the plurality ofenergy storage devices is disposed, and each of the plurality of energystorage devices is in contact with the layer of support material. 25.The energy storage assembly of claim 1, wherein the plurality of storagedevices are electrically connected to one another through electricalconnections printed on the layer of material.